One-sided circuit board for multi-layer printed wiring board, multi-layer printed wiring board, and method of its production

ABSTRACT

A single-sided circuit substrate for a multilayer printed writing board has an insulating hard substrate, a conductor circuit formed on a surface of the substrate, an adhesive layer formed on the other surface, and at least one viahole through the substrate and the adhesive layer so as to pass these layers and contact with the conductor. The viaholes are filled with conductive paste. The invention also provides a multilayer printed wiring board having an IVH structure constituted with single-sided circuit hard substrates and a method of efficiently manufacturing the same with high yield.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to a single-sided circuit substrate for amultilayer printed wiring board, a multilayer printed wiring board and amethod of manufacturing the same, and more particularly, it proposes asingle-sided circuit board to be developed for manufacturing amultilayer printed wiring board having an interstitial-viahole structurein higher yield and efficiency, and a multilayer printed wiring boardproduced by laminating a plurality of such single-sided circuit boards,and a method of manufacturing the same.

2. Description of Background Information

The conventional multilayer printed wiring board is a multilayered bodyconstituted by alternately building up copper-clad laminates andprepregs. This multilayered body has a surface wiring pattern on anouter surface thereof, and has an innerlayer wiring pattern between itsinterlaminar layers. These wiring patterns are electrically connectedvia through-holes formed in the multilayered body in a thicknessdirection thereof between the mutual innerlayer wiring patterns, orbetween the innerlayer wiring pattern and the surface wiring pattern.

However, in the multilayer printed wiring board having theabove-mentioned through-hole structure, it is required to ensure aregion for the formation of the through-holes, so that it is difficultto attain a high densification of mounting parts and hence there aredisadvantages that it is not able to fully meet the requirements ofsuper-miniaturization of portable electric equipments and practicalapplication of the narrow-pitched packages and MCM (Multi Chip Module).

Recently, instead of the multilayer printed wiring board with thethrough-hole structure as mentioned above, a multilayer printed wiringboard having an interstitial-viahole (IVH) structure has been noticed,which is suitable for the miniaturization and high densification of theelectric equipment.

The multilayer printed wiring board having the IVH structure is aprinted wiring board having such a structure that conductive viaholesconnecting conductor layers to each other are arranged in each of theinterlaminar insulating layers forming the multilayered body. That is,in such wiring board, electrical connection between the mutualinnerlayer wiring patterns or between the innerlayer wiring pattern andthe surface wiring pattern is made through viaholes (buried viaholes orblind viaholes) not passing the wiring substrate. Therefore, in themultilayer printed wiring board having the IVH structure, it is notrequired to provide specific region for the formation of thethrough-holes, and hence the miniaturization and high densification ofthe electric equipment can easily be attained.

As to the multilayer printed wiring board having the IVH structure,there is reported a proposal for the development of the multilayerprinted wiring board having the IVH structure for all layers, forinstance, on page 57 of “The 9th National Convention Record JIPC (Mar.2, 1995)” or a draft collection for 9th Circuit Packaging AcademicLecture. The multilayer printed wiring board according to this proposalis developed on the basis of {circle around (1)} high-speed drillingtechnique of minute viaholes by carbon dioxide gas laser, {circle around(2)} adoption of a composite material of aramide nonwoven fabric andepoxy resin as a substrate material, and {circle around (3)}interlaminar connecting technique by filling of a conductive paste, andmanufactured by the following processes.

At first, an aramide nonwoven fabric impregnated with epoxy resin isused as a prepreg and hole drilling through carbon dioxide gas laser isapplied to the prepreg, and then a conductive paste is filled in theresulting hole portions (see FIG. 1(a)).

Next, copper foils are put on both surfaces of of the prepreg, andpressed under heating through heat press. Thus, the epoxy resin in theprepreg and the conductive paste are hardened to provide an electricalconnection between the copper foils put on both surfaces of the prepreg(see FIG. 1(b)).

And then, patterning is carried out onto the copper foils by an etchingprocess to provide double-sided hard substrate having viaholes (see FIG.1(c)).

The formation of multilayers is carried out by using the double-sidedsubstrate as a core layer. Concretely, the prepreg filled with the aboveconductive paste and the copper foil are successively laminated on bothsurfaces of the core layer while positioning and again heat-pressed andthen the copper foil of the outermost layer is etched to provide afour-layer substrate (see FIGS. 1(d), (e)). If it is intended to furtherconduct the formation of the multilayer, the above steps are repeated toobtain a six or eight-layer substrate.

The drawback of the above conventional technique is that the productionsteps become complicated and a long time is taken for the productionbecause the heating and pressing through hot press and the patterningstep of the copper foil through etching should be repeated at any numberof times.

In the multilayer printed wiring board having the IVH structure obtainedby the above production method, it is difficult to confirm the poorpatterning of the copper foil in the production course, so that if thepoor patterning is caused even at one place (one step) in the productioncourse, the whole of the wiring board as a final product becomesinferior.

That is, the above conventional production process has a fatal drawbackthat the degradation of production efficiency or production yield isliable to be caused because if inferior good is produced even at oneplace among the lamination steps, good products made in the otherlamination steps should be removed.

It is an object of the invention to provide a single-sided circuitsubstrate for multilayer printed wiring board developed for efficientlymanufacturing a multilayer printed wiring board having an IVH structurein a high yield.

It is another object of the invention to provide a multilayer printedwiring board having an IVH structure constituted with the abovesingle-sided circuit substrates.

It is the other object of the invention to propose a method ofefficiently manufacturing the multilayer printed wiring board having theIVH structure in a higher yield by using the single-sided circuitsubstrates.

SUMMARY OF THE INVENTION

The inventors have made various studies for achieving the above objects,and as a result the invention having the following features andconstruction has been accomplished.

(1) As a single-sided circuit substrate for a multilayer printed wiringboard used for efficiently manufacturing a multilayer printed wiringboard having an IVH structure in a high yield, the invention provides asingle-sided circuit board for a multilayer printed wiring boardcomprising an insulating hard substrate, a conductor circuit formed on asurface of the substrate and an adhesive layer formed respectively onthe other surface of the substrate, in which holes contacting with theconductor are formed in the substrate and the adhesive layer and aconductive paste is filled therein to form viaholes.

Here, the conductor circuit is desirable to be formed by etching acopper foil of a single-sided copper-clad laminate.

(2) As a multilayer printed wiring board having an IVH structurecomprised of the single-sided circuit board described of the above item(1), the invention provides a multilayer printed wiring board having astructure that laminated circuit substrates are electrically connectedto each other through interstitial viaholes, characterized in that atleast one layer of the circuit substrates is a single-sided circuitsubstrate comprising an insulating hard substrate, a conductor circuitformed on a surface of the substrate and an adhesive layer formedrespectively on the other surface of the substrate, in which holescontacting with the conductor are formed in the substrate and theadhesive layer and a conductive paste is filled therein to formviaholes.

Here, the conductor circuit is desirable to be formed by etching acopper foil of a single-sided copper-clad laminate.

(3) As a method of efficiently manufacturing a multilayer printed wiringboard having an IVH structure in a high yield by using the single-sidedcircuit board of the item (1), the invention provides a method ofmanufacturing a multilayer printed wiring board comprising the steps of:

{circle around (1)} a step of forming a conductor circuit by etching ametal foil adhered to a surface of an insulating hard substrate;

{circle around (2)} a step of forming an adhesive layer on a surfaceopposite to the conductor circuit formed on the surface of thesubstrate;

{circle around (3)} a step of forming holes contacting with a conductorin the insulating hard substrate and the adhesive layer and filling aconductive paste in the holes to provide a single-sided circuit board;and

{circle around (4)} a step of piling two or more of the single-sidedcircuit substrates one upon the other or piling the single-sided circuitsubstrate upon another circuit substrate and then pressing them at oncethrough the adhesive layer provided on the substrate in a multilayerform.

Here, it is preferable to form the holes passing through the insulatinghard substrate and the adhesive layer and contacting with the conductorby irradiation of a laser.

And also, the conductor circuit is desirable to be formed etching acopper foil of a single-sided copper clad laminate formed by theadhesion of the copper foil to one surface of the insulating hardsubstrate.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1(a)-1(e) are diagrammatically sectional views illustratingmanufacture steps of a multilayer printed wiring board according to theconventional technique.

FIG. 2 is a diagrammatically section view of an embodiment of themultilayer printed wiring board according to the invention.

FIG. 3 is a diagrammatically section view illustrating manufacture stepsof a single-sided circuit substrate used for the manufacture of theabove multilayer printed wiring board.

FIG. 4 is a diagrammatically section view illustrating an embodiment ofsteps combining the single-sided circuit substrates in the manufactureof the above multilayer printed wiring board.

FIG. 5 is a diagrammatically partial section view illustratingmanufacture steps of another single-sided circuit substrate used for themanufacture of the multilayer printed wiring board.

FIG. 6 is a diagrammatically partial section view of another embodimentof the multilayer printed wiring board according to the invention.

In the figures, numeral 1 is a multilayer printed wiring board; 2 a, 2b, 2 c, 2 d insulating hard substrates; 3 a, 3 b, 3 c, 3 d conductorcircuits; 4 a, 4 b, 4 c, 4 d adhesive layers; 5 a conductive paste; 6 a,6 b, 6 c viaholes; 7 a, 7 b, 7 c, 7 d single-sided circuit substrates; 8a chip component; 9 a solder; 12 a, 12 b, 12 c, 12 d insulating hardsubstrates; 13 a metal foil; 13 a, 13 b, 13 c, 13 d conductor circuits;14 a, 14 b, 14 c, 14 d adhesive layers; 16 a hole; 17 a, 17 b, 17 c, 17d single-sided circuit substrates; 18 a conductor circuit at the bottomof the hole; 21 another embodiment of the multilayer printed wiringboard; 22 the other embodiment of the insulating hard substrate; 23 theother embodiment of the conductor circuit; 24 the other embodiment ofthe adhesive layer; 25 the other embodiment of the through-hole; and 26another embodiment of the viahole.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS OF THE INVENTION

The single-sided circuit substrate for the multilayer printed wiringboard according to the invention comprises an insulating hard substrate,a conductor circuit formed on a surface of the substrate and an adhesivelayer formed respectively on the other surface of the substrate, inwhich holes contacting with the conductor are formed in the substrateand the adhesive layer and a conductive paste is filled therein to formviaholes.

The adhesive layer constituting the single-sided circuit substrate forthe multilayer printed wiring board plays a role of adhering the abovesingle-sided circuit substrates to each other or the above single-sidedcircuit substrate to another circuit substrate in the manufacture of themultilayer printed wiring board having an IVH structure.

The viahole constituting the single-sided circuit substrate for themultilayer printed wiring board plays a role of electrically connectingthe conductor circuit of the above single-sided circuit substrate to aconductor circuit of another circuit substrate to be laminated in themanufacture of the multilayer printed circuit board having the IVHstructure. Particularly, the conductive paste filled in the holespassing the insulating hard substrate and the adhesive layer andcontacting with the conductor circuit adheres to the conductor circuitof the other adjoining circuit substrate to be laminated bythermosetting and electrically connects to the respective conductorcircuit.

The conductor circuits constituting the single-sided circuit substratefor the multilayer printing wiring board are a surface wiring pattern oran innerlayer wiring pattern constituting the multilayer printed wiringboard having the IVH structure. Such conductor circuits are formed byetching the metal foil adhered to one surface of the insulating hardsubstrate, and preferably formed by etching a copper foil of asingle-sided copper-clad laminate obtained by laminating the copper foilonto the one surface of the insulating hard substrate.

The multilayer printed wiring board having the IVH structure canefficiently be manufactured in a higher yield by utilizing thesingle-sided circuit board having the structure as mentioned above.

The method of manufacturing the multilayer printed wiring board by usingthe above single-sided circuit substrate according to the invention willbe described below. That is, the method of the invention ischaracterized by the following steps:

{circle around (1)} a step of forming a conductor circuit by etching ametal foil adhered to a surface of an insulating hard substrate;

{circle around (2)} a step of forming an adhesive layer on a surfaceopposite to the conductor circuit formed on the surface of thesubstrate;

{circle around (3)} a step of forming holes contacting with a conductorin the insulating hard substrate and the adhesive layer and filling aconductive paste in the holes to provide a single-sided circuit board;and

{circle around (4)} a step of piling two or more of the single-sidedcircuit substrates one upon the other or piling the single-sided circuitsubstrate upon another circuit substrate and then pressing them at oncethrough the adhesive layer provided on the substrate in a multilayerform.

Thus, the method of manufacturing the multilayer printed wiring boardaccording to the invention lies in a feature that the single-sidedcircuit substrates having the conductor circuits forming a given wiringpattern are previously manufactured individually. Therefore, thepresence or absence of inferior place of the conductor circuits can beconfirmed in these single-sided circuit substrates before thelamination, so that only the single-sided circuit substrates having noinferior place can be used at the lamination stage. As a result,according to the method of the invention, the occurrence of inferiorproduct decreases at the manufacture stage and hence the multilayerprinted wiring board having the IVH structure can be manufactured in ahigher yield.

Further, according to the method of manufacturing the multilayer printedwiring board according to the invention, it is not required to repeatthe step of laminating prepregs and pressing them under heating as inthe conventional technique and the single-sided circuit substrate can bepiled on another circuit substrate and integrally united with each otherthrough hot pressing at once by utilizing the adhesive layer formed onthe single-sided circuit substrate. That is, according to the method ofthe invention, the multilayer printed wiring board having the IVHstructure can efficiently be manufactured in a short time withoutrepeating the complicated steps.

In the above method of the invention, it is desirable to form the holespassing the insulating hard substrate and the adhesive layer andcontacting with the conductors by irradiation of a laser. Because, asthe hole for the formation of the viahole in the single-sided circuitsubstrate, it is advantageous to form holes having a fine size at a highdensity as far as possible, and the application of laser as a holedrilling technique can easily form the holes having a fine size at thehigh density.

Further, holes passing only the insulating hard substrate and theadhesive layer can be formed by the drilling technique through the laserwithout damaging the conductor circuit. As a result, the holes areformed at a state of closing one end with the conductor circuit areformed without the formation of the holes passing the prepreg substrateas in the conventional technique, so that the conductive paste is filledin the resulting holes to form a face contact between the viahole andthe conductor circuit, whereby a sure connection is obtained.

Thus the manufactured multilayer printed wiring board having the IVHstructure according to the invention is characterized in that at leastone layer of the circuit substrates constituting the wiring board is asingle-sided circuit substrate comprising an insulating hard substrate,a conductor circuit formed on a surface of the substrate and an adhesivelayer formed respectively on the other surface of the substrate, inwhich holes contacting with the conductor are formed in the substrateand the adhesive layer and a conductive paste is filled therein to formviaholes.

Here, the single-sided circuit substrate constituting the multilayerprinted wiring board according to the invention is adhered to anothercircuit substrate through the adhesive layer. As such another circuitsubstrate, use may be made of the single-sided circuit substrateaccording to the invention and the conventionally known printed wiringsubstrate.

Moreover, the multilayer printed wiring board according to the inventionmay be subjected to various treatments usually made in the printedwiring board such as formation of solder resist on the surface,nickel/gold plating or soldering to the surface wiring pattern, holedrilling, cavity treatment, plating of through-hole and the like.

Furthermore, the multilayer printed wiring board according to theinvention is used for mounting an electronic component such as ICpackage, bare chip, chip component or the like.

EXAMPLE

FIG. 2 is a diagrammatically section view of an embodiment of themultilayer printed wiring board according to the invention. In thisfigure, the multilayer printed wiring board 1 is a four layer boardformed by laminating single-sided circuit substrates 7 a, 7 b, 7 c, 7 d,which consist of insulating hard substrates 2 a, 2 b, 2 c, 2 d andconductor circuits 3 a, 3 b, 3 c, 3 d formed by etching a metal foiladhered to a surface of the substrate, adhesive layers 4 a, 4 b, 4 c, 4d each formed on a surface of the substrate opposite to the conductorcircuit and viaholes 6 a, 6 b, 6 d formed by filling a conductive paste5 in holes passing the insulating hard substrates 2 a, 2 b, 2 c, 2 d andthe adhesive layers 4 a, 4 b, 4 c, 4 d and contacting with the conductorcircuits 3 a, 3 b, 3 c, 3 d, and mutually joining them through theadhesive layers 4 a, 4 b, 4 c, 4 d formed on the single-sided circuitsubstrates 7 a, 7 b, 7 c, 7 d, respectively.

In this case, the conductor circuit 3 a of the single-sided circuitsubstrate 7 a and the conductor circuit 3 d of the single-sided circuitsubstrate 7 d are formed into a given wiring pattern, respectively, andarranged on upper surface and lower surface of the multilayer printedwiring board 1 as a surface wiring pattern. And also, the conductorcircuit 3 b of the single-sided circuit substrate 7 b and the conductorcircuit 3 c of the single-sided circuit substrate 7 c are formed into agiven wiring pattern, respectively, and arranged on a lower side of thesingle-sided circuit substrate 7 a and on an upper side of thesingle-sided circuit substrate 7 d in the multilayer printed wiringboard 1 as an innerlayer wiring pattern.

Moreover, it is favorable that the conductor circuits 3 a, 3 b, 3 c, 3 dare formed by etching a copper foil of a single-sided copper cladlaminate provided by forming the copper foil on, for example, a surfaceof the insulating hard substrates 2 a, 2 b, 2 c, 2 d.

And also, the viahole 6 a is formed by passing through the insulatinghard substrate 2 a and the adhesive layer 4 a in a thickness direction,and the viahole 6 b is formed by passing through the insulating hardsubstrates 2 b, 2 c and the adhesive layers 4 b, 4 c in a thicknessdirection, and the viahole 6 d is formed by passing through theinsulating hard substrate 2 d and the adhesive layer 4 d in a thicknessdirection, and the conductive paste 5 is filled in each of theseviaholes. Among these viaholes, the viahole 6 a is a blind viaholeelectrically connecting the conductor circuit 3 a as the surface wiringpattern to the conductor circuit 3 b as the innerlayer wiring pattern,and the viahole 6 b is a buried viahole electrically connecting theconductor circuits 3 b, 3 c to each other as the innerlayer wiringpattern, and the viahole 6 d is a blind viahole electrically connectingthe conductor circuit 3 c as the innerlayer wiring pattern to theconductor circuit 3 d as a surface wiring pattern. They are interstitialviaholes.

As the insulating hard substrate 2 a, 2 b, 2 c, 2 d, use may be made ofa substrate formed by curing, for example, glass cloth epoxy resin,glass nonwoven cloth epoxy resin, glass cloth bismaleimide triazineresin, aramide nonwoven cloth epoxy resin or the like in form of aplate.

The adhesive layer 4 a, 4 b, 4 c, 4 d may be constituted with a resinadhesive such as epoxy resin, polyimide, bismaleimide triazine, acrylicresin, phenolic resin or the like.

As the conductive paste, use may be made of conductive paste of, forexample, copper, silver, gold, carbon or the like.

Various electronic components may be mounted onto the multilayer printedwiring board according to the invention. For example, as shown by aphantom line in FIG. 2, a chip component such as IC package, bare chipor the like may be placed on a given position of the surface wiringpattern 3 a and fixed thereto with a solder 9.

The method of manufacturing the multilayer printed wiring boardaccording to the invention shown in FIG. 2 will be described below.

(1) At first, a single-sided circuit substrate 7 a (17 a) according tothe invention constituting the multilayer printed wiring board 1 of FIG.2 is prepared. It will concretely be described with reference to FIG. 3.

{circle around (1)} There is provided an insulating hard substrate 12 aadhered on a surface with a metal foil 13 as shown in FIG. 3(a). Forinstance, it is advantageous to use a one-sided copper-clad laminate asthe insulating hard substrate 12 a provided on the surface with themetal foil 13.

{circle around (2)} Next, the metal foil 13 is etched into a givenpattern as shown in FIG. 3(b), whereby conductor circuits 13 a areformed. Moreover, the well-known usual means can be adopted as theetching method. The conductor circuits 13 a are arranged as a surfacewiring pattern. If the conductor circuits are arranged as an innerlayerwiring pattern, in order to improve the adhesion property between thelayers, the surface of the conductor circuit is advanatgeous to beroughened by using a well-known means such as micro-etching, rougheningplating, application of both-surface roughened copper foil or the like.

{circle around (3)} Then, an adhesive layer 14 a is formed on a surfaceof the insulating hard substrate 12 a having the conductor circuits 13 aopposite to the conductor circuit as shown in FIG. 3(c). The adhesivelayer 14 a may be formed by applying a given resin adhesive by means ofa roll coater, curtain coater, spray coater, screen printing or the likeand then precuring, or by laminating an adhesive sheet. In this case,the thickness of the adhesive layer is advantageously within a range of10˜50 μm.

{circle around (4)} Next, holes 16 are formed so as to pass the adhesivelayer 14 a and the insulating hard substrate 12 a in a thicknessdirection and contact with a conductor as shown in FIG. 3(d). It ispreferable to form the holes 16 by irradiating a laser to the insulatinghard substrate 12 a from a side of the adhesive layer 14 a. As thedrilling machine irradiating a laser can be used, for example, apulseoscillation type carbon dioxide gas laser drilling machine. Thus,holes having a microsize of 60˜200 μmφ can be formed in a high accuracyby using the carbon dioxide gas laser drilling machine. As a result, itis possible to form viaholes in a high density and a multilayer printedwiring board having a small size and a high density can be manufactured.

According to the drilling method irradiating the laser, holes can bedrilled in only the adhesive layer 14 a and portions of the insulatinghard substrate 12 a without damaging the conductor circuit 13 a, so thatthe resulting holes 16 are opened only at the side of the adhesive layer14 a and closed with the conductor circuit at the other end. Thus, theelectrical connection between the viahole and the conductor circuit 13 acan surely be attained. Moreover, desmear treatment may be applied inorder to clean the surface 18 of the conductor circuit at the bottom ofthe hole 16.

{circle around (5)} Then, as shown in FIG. 3(e), a conductive paste 5 isfilled in the hole 16 to prepare a single-sided circuit substrate 17 a.As the method of filling the conductive paste 5, there can be adopted ascreen printing method using, for example, a metal mask. In order toform the viahole in a high accuracy in the filling, it is advantageousto previously form a protection mask around the hole 16. The protectionmask may be formed by laminating a film or a paper on the surface of theadhesive layer 14 a and drilling together in the formation of the hole.And also, it is advantageous that the conductive paste is filled to anextend somewhat exceeding over the hole 16 in order to realize theviahole having a good electrical connection to the conductor circuit asan innerlayer of another circuit substrate to be laminated. Moreover, itis advantageous to precure the filled conductive paste for enhancing theworking efficiency of subsequent steps, and the protection mask ispeeled off before the lamination.

(2) Single-sided circuit substrates 17 b, 17 c, 17 d as shown in FIG. 4comprising insulating hard substrates 12 b, 12 c, 12 d and conductorcircuits 13 b, 13 c, 13 d formed on a surface of the substrate, adhesivelayers 14 b, 14 c, 14 d formed on the other surface and viaholes formingholes 16 passing the insulating hard substrate and the adhesive layersand contacting with the conductor and filling the conductive paste 5therein are prepared at the same steps as mentioned above.

(3) Then, the above single-sided circuit substrates 17 a, 17 b, 17 c, 17d are piled one upon the other in given order while positioning withguide holes and guide pins arranged on the peripheral portions of thesingle-sided circuit boards. In this case, the conductor circuit 13 c ofthe single-sided circuit substrate 17 c is piled on the adhesive layer14 d of the single-sided circuit substrate 17 d, and the adhesive layer14 b of the single-sided circuit substrate 17 b is piled on the adhesivelayer 14 c, and the adhesive layer 14 a of the single-sided circuitsubstrate 17 a is piled on the conductor circuit 13 b.

(4) After the single-sided circuit substrates are piled in this way,they are heated and pressed within a temperature range of 140° C.˜200°C. with a hot press, whereby these single-sided circuit substrates arepressed and integrally united in form of a multilayer at once.

In this step, the single-sided circuit substrates 17 a, 17 b, 17 c, 17 dpiled one upon the other through the adhesive layers 14 a, 14 b, 14 c,14 d are integrally united in form of the multilayer by thermosettingthe adhesive layers 14 a, 14 b, 14 c, 14 d at a closed state. At thesame time, the conductive paste is thermoset at a state of closing tothe respective conductor circuit to form the viaholes, whereby themultilayer printed wiring board 1 is obtained.

ANOTHER EXAMPLE

(1) Although the multilayer printed wiring board comprised of foursingle-sided circuit substrates is described in the above example, theinvention can be similarly applied to a case of three layer or highermultilayer of 5 or more layers, or can manufacture multilayer printedwiring board by laminating the single-sided circuit substrate accordingto the invention onto a single-sided printed substrate, both-sidedprinted substrate, both-sided through-hole printed substrate ormultilayer printed substrate produced by the conventional method.

(2) Although the drilling for making the holes for the formation of theviahole is carried out by irradiating laser in the above example, amechanical means such as drilling, punching or the like may be applied.The method of manufacturing the single-sided circuit substrate and themultilayer printed wiring board of the latter case will be describedwith reference to FIGS. 5 and 6.

{circle around (1)} At first, as shown in FIG. 5(a), a conductor circuit23 is formed on an insulating hard substrate 22 by etching a metal foiladhered onto a surface of the substrate, and an adhesive layer 24 isformed on a surface of the substrate opposite to the conductor circuit23.

{circle around (2)} Next, a through-hole 25 is formed by means of amechanical means such as drilling, punching or the like as shown in FIG.5(b) and a conductive paste 5 is filled in the through-hole 25 toprepare a single-sided circuit substrate. In this case, it isadvantageous that the conductive paste 5 is filled to an extent somewhatexceeding over the through-hole 25 for providing the viahole having agood connection to a conductor circuit of another circuit substrate tobe connected as shown in FIG. 5(c).

{circle around (3)} Then, a multilayer printed wiring board 21 havingviaholes 26 as shown in FIG. 6 is obtained by piling a plurality of thesingle-sided circuit substrates one upon the other and integrallyuniting them in the same manner as described above.

(3) In the multilayer printed wiring board according to the invention,the surface wiring pattern may be formed only in form of pads formounting a chip electronic component.

As mentioned above, the single-sided circuit substrate for themultilayer printed wiring board according to the invention canefficiently manufacture a high-density multilayer printed wiring boardhaving an IVH structure in a high yield by using such single-sidedcircuit boards and integrally uniting them in a multilayer form throughpressing at once because it is subjected to a given treatment and has anadhesive layer.

And also, according to the method of manufacturing the multilayerprinted wiring board according to the invention using the abovesingle-sided circuit substrate, only the single-sided circuit substrateshaving no defect are joined through the adhesive layer formed on thesubstrate, so that the high-density multilayer printed wiring boardhaving the IVH structure can efficiently be manufactured in a high yieldwithout adopting the complicated method having many repeating steps asin the conventional technique.

Furthermore, the multilayer printed wiring board according to theinvention constituted with the single-sided circuit boards has astructure that the single-sided circuit substrates are joined throughthe adhesive layer, so that it can easily be provided as thehigh-density multilayer printed wiring board having the IVH structurewithout adopting the complicated method having many repeating steps asin the conventional technique.

What is claimed is:
 1. A single-sided circuit board for a multilayerprinted wiring board comprising: a single-sided copper clad laminatehaving an insulating hard substrate and a copper foil adhered on asurface of the substrate, a conductor circuit pattern formed on thesurface of the substrate by etching the copper foil of the copper cladlaminate, a resin adhesive layer formed on the other surface of thesubstrate, and conductive paste filled in holes formed through thesubstrate and adhesive layer so as to be in contact with the conductorcircuit pattern to provide viaholes.
 2. The slngle-sided circuit boardaccording to claim 1 wherein said insulating hard substrate comprises atleast one member selected from glass cloth epoxy resin, glass nonwovencloth epoxy resin, glass cloth bismaleimide triazine resin, and aramidenonwoven cloth epoxy resin.
 3. The single-sided circuit board accordingto claim 2 wherein said insulting hard substrate comprises at least oneof glass cloth epoxy resin, glass nonwoven cloth epoxy resin, glasscloth bismaleimide triazine resin, and aramide nonwoven cloth epoxyresin in the form of a plate.
 4. The single-sided circuit boardaccording to claim 1 wherein said insulating hard substrate comprisesglass cloth epoxy resin.
 5. The single-sided circuit board according toclaim 1 wherein said insulating hard substrate comprises glass nonwovencloth epoxy resin.
 6. The single-sided circuit board according to claim1 wherein said insulating hard substrate comprises glass clothbismaleimide triazine resin.
 7. The single-sided circuit board accordingto claim 1 wherein said insulating hard substrate comprises aramidenonwoven cloth epoxy resin.
 8. The single-sided circuit board accordingto claim 1 wherein said resin adhesive layer is made from at least oneof epoxy resin, polyimide, bismaleimide triazine, acrylic resin, andphenolic resin.
 9. The single-sided circuit board according to claim 1wherein said conductive pastes are made of at least one of copper,silver, gold, and carbon.
 10. The single-sided circuit board accordingto claim 1 wherein said resin adhesive layer has a thickness of 10 to 50micron.
 11. A multilayer printed wiring board having a plurality ofwiling substrates which are laminated and electrically connected to eachother through interstitial viaholes, comprising: at least one of thewiring substrates being formed by a single-sided circuit board, whereinsaid single-sided circuit board having an insulating hard substrate anda copper foil adhered on the substrate, a conductor circuit patternformed on a surface of the substrate by etching the copper foil of thecopper clad laminate, a resin adhesive layer formed on the other surfaceof the substrate, and conductive paste filled in holes through thesubstrate and adhesive layer to be in contact with the conductor circuitpattern to provide viaholes.
 12. A method of manufacturing a multilayerprinted wiring board comprising: forming a conductor circuit pattern ona surface of a single-sided copper clad laminate having an insulatinghard substrate and a copper foil adhered on the substrate by etching thecopper foil; forming a resin adhesive layer on an opposite surface ofthe substrate; forming holes penetrating through the hard substrate andresin adhesive layer so as to be in contact with the conductor circuitpatterns; filling conductive paste in the holes to provide asingle-sided circuit board with viaholes; piling two or more of thesingle-sided circuit boards one upon the other or piling thesingle-sided circuit board upon another circuit board to provide piledsingle-sided circuit boards; and pressing the piled single-sided circuitboards at once through the resin adhesive layer into a multilayer form.13. The method according to claim 12 wherein the piled single-sidedcircuit boards are hot-pressed together.
 14. The method according toclaim 12 wherein the piled single-sided circuit boards are hot-pressedtogether to integrally unite the single-sided circuit boards.